This invention relates to a display device operating in accordance with a reset principle. The device comprises an electro-optical display medium between two supporting plates, a system of pixels arranged in rows and columns, with each pixel being constituted by picture electrodes arranged on the facing surfaces of the supporting plates, and a system of row and column electrodes for presenting selection and data signals by means of which a range of voltages dependent on the electro-optical display medium can be presented across the pixels for the purpose of picture display. The picture electrodes on one of the supporting plates are connected in an electrically conducting manner via a first switching unit to a column electrode for data signals, and via a second switching unit to an auxiliary voltage for applying auxiliary voltage across the pixels prior to selection, said auxiliary voltage lying beyond or on the limit of the range to be used for picture display.
A display device of this type is suitable for displaying alpha-numerical information and video information by means of passive electro-optical display media such as liquid crystals, electrophoretic suspensions and electrochromic materials.
A display device of the type described in the opening paragraph and operative in accordance with the reset principle is known from U.S. Pat. No. 5,032,831 (Jul. 16, 1991), and which is hereby incorporated by reference. In a device shown in this patent, diodes are used as non-linear switching elements in an active matrix. Two juxtaposed columns of pixels are connected via these diodes to an intermediate auxiliary voltage electrode for applying the auxiliary voltage, while the drive electrodes (column electrodes) are always arranged pairwise between two columns of pixels, offset over the width of a column with respect to the auxiliary voltage electrode. Therefore (apart from the space for the switching elements) space for one electrode or for two electrodes is left between successive columns of picture electrodes. This arrangement, with a spatial frequency of 2 rows of columns, has an unfavourable influence on the display due to the occurrence of so-called artifacts. This can be prevented by providing a black mask or black strips over the electrodes. However since the width of the black strips is determined by the largest distance which must be covered (in this case the space which is required for two column electrodes), these strips unnecessarily cover parts of the picture electrode at other areas.
Moreover, it is often desirable to provide black material at the area of the diodes. These diodes are usually made of amorphous silicon which has a larger leakage current under the influence of light. Without any special measures, a large part of the surface area of the display device is therefore lost for picture display.